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The Normalised Kumaraswamy Breakage Function (NKBF), developed previously to describe First Break milling of wheat kernels, was applied here to describe the breakage of the stocks produced by First Break that then pass to Second Break milling. The breakage equation for roller milling assumes independent breakage of particles as they pass through the mill; that assumption was tested for Second Break milling and found to be appropriate. A single NKBF was not adequate to describe the full particle size distribution (PSD) created by Second Break milling, as the PSD is bimodal, and the NKBF is unimodal. Instead, the PSD was divided into the fraction of particles larger than 2000 μm, and those smaller than 2000 μm, and separate NKBF functions were applied to each fraction. In this way, it was demonstrated that the size distribution of particles larger than 2000 μm produced after Second Break milling depended strongly on the input particle size, but was essentially independent of the roll gap used for Second Break. By contrast, the PSD of particles smaller than 2000 μm depended strongly on the roll gap, but was essentially independent of the input particle size. This finding reflects the nature of Second Break milling, that it involves scraping endosperm material off bran particles, such that the endosperm material (which is produced as small particles) depends strongly on the size of the gap through which the bran particle passes, but the bran particle itself remains essentially intact, irrespective of roll gap. This scraping of endosperm particles, although strongly dependent on the roll gap, is independent of the size of the bran particles, because the bran particles pass through the roll gap oriented along their longest dimensions. Second Break milling of the entire output from First Break, as practised in double high systems, could be described adequately by a single NKBF. Extending the breakage equation via the NKBF to Second Break facilitates the application of simulation and optimisation to flour milling for both food and non-food processes.

A simplified model describing wheat breakage during roller milling is presented. Previous work introduced the breakage equation describing First Break roller milling of wheat in terms of a breakage function that incorporated relevant input and processing parameters such as roll gap, kernel diameter and kernel hardness. The resulting empirical function, based on polynomial fits, was sufficiently flexible to describe the range of particle size distributions encountered in typical milling operations, but contained a high number of coefficients, making the interpretation of the physical significance of the coefficients difficult and requiring an excessive amount of experimental data. The current work simplifies the breakage function by normalising the output particle size distribution against the milling ratio raised to a power. The Kumaraswamy probability distribution function is then used to describe the normalised data obtained following First Break milling of a wide range of wheat at different roll gaps under both Sharp-to-Sharp and Dull-to-Dull roll dispositions. Using this approach, the effects of roll gap and kernel diameter on wheat breakage can be described using just four parameters. This simplified equation is more practical and versatile for implementation in process integration strategies for the purpose of design and optimisation of cereal processes for food and non-food uses.

This study investigated the economic feasibility of co-producing an arabinoxylan (AX) product with ethanol from wheat, in order to establish whether, under plausible scenarios, it was realistic that a commercial source of wheat AX could be established. The possibility of recovering wheat bran via pearling was also investigated, both as an opportunity to have bran bypass the main ethanol production process and enter the distillers dried grain with solubles (DDGS) co-product in a dry state, or as a means of obtaining bran for AX extraction. Process flowsheets describing three scenarios were created using SuperPro Designer: conventional wheat-to-bioethanol production with DDGS as the principal co-product; bioethanol production with co-production of AX using conventional hammer milling and sieving to recover the bran for AX extraction; and the use of pearling technology to recover bran for AX extraction. Full economic analysis of each of the three scenarios, considering all capital and operating costs, was undertaken, basing comparisons on a constant return on investment in order to estimate the production costs of AX. Sending bran removed via pearling directly to DDGS was not economic; the reduced ethanol yield and increased electricity costs more than offset the savings in drying costs. Simulation of the integrated processes indicated that an AX product of 80% purity could be co-produced with ethanol at a cost of around 3.7–4.5£/kg. This is within the range of comparable viscosity-enhancing ingredients used in the food industry, but is towards the top end of the range. In order to establish a market, AX would therefore need to offer some additional functionality. AX production from bran obtained via pearling was more expensive that from bran obtained via hammer milling and sieving; however, whether the functionality of the AX differs needs to be established. The research indicates that creating a market for AX is feasible in terms of production costs if the AX is co-produced with ethanol. On this basis, further research is justified to investigate the functionality of AX from different sources, to optimise the AX extraction process and to establish the potential of AX as a food or pharmaceutical ingredient.

Arabinoxylans (AX) are a component of wheat bran that could have application as a food ingredient or for non-food uses if a commercial source could be established at a reasonable price. AX can be co-produced with ethanol in an integrated process, which could enhance the economics of a wheat-based biorefinery principally producing ethanol, and thus facilitate the introduction of commercial wheat-based fuel ethanol production in the UK. A study was therefore undertaken to investigate the economic feasibility of co-producing AX with ethanol from wheat. Pearling is an advanced wheat fractionation technology that preferentially recovers bran from the outer layers of the wheat kernel. The practical feasibility and economic benefit of recovering wheat bran for AX extraction via pearling was also investigated. This paper describes experimental studies to investigate the AX content in bran fractions obtained by pearling, the yields of AX extracted from pearling fractions, and the feasibility of recovering starch from the removed bran via washing, in order to minimise the reduction in ethanol yield due to starch losses with the bran. The following paper describes simulation and economic analysis of ethanol–AX co-production with and without the use of pearling to obtain the bran for AX extraction. AX was more concentrated in the outer bran layers of the wheat kernel, and the yield and purity of AX extracted from pearling fractions of these layers were greater than for fractions arising from the inner bran layers. This suggests that recovery of bran for AX extraction by pearling would give advantages in terms of yield. However, the quality and functionality of the AX extracted from the outer bran layers, compared with AX arising from other parts of the wheat kernel, need to be investigated. Enzyme treatment of AX extracts significantly enhanced the purity of the extracts. Washing bran with water prior to AX extraction resulted in 71–77% starch recovery for return to the ethanol production section.

The effects of wheat properties on breakage during First Break roller milling, as described by the Double Normalised Kumaraswamy Breakage Function (DNKBF), were investigated. A set of 45 wheats from nine varieties representing the range of commercial varieties grown in the UK, and grown over three harvest years at several nitrogen fertiliser levels, were milled at five roll gaps under Sharp-to-Sharp and Dull-to-Dull dispositions. The resulting particle size distributions were fitted with a DNKBF in order to understand the physical significance of the DNKBF parameters and to relate them to shape and hardness. The DNKBF parameters related strongly to hardness as measured using either the Single Kernel Characterisation System or Particle Size Index, allowing the particle size distribution over the range 0–4000 μm to be predicted solely from wheat hardness. A residual analysis showed that the remaining variation was correlated with kernel mass, and that more elongated kernels break to give slightly larger particles than more spherical kernels of equivalent hardness. Two types of breakage are identified, one of which principally produces many small endosperm particles along with large bran particles, while the other tends to produce mid-sized particles. The former dominates under Dull-to-Dull milling and for soft wheats, while the latter becomes more prominent under Sharp-to-Sharp milling and for harder wheats.

A value analysis methodology [Sadhukhan, J., Zhang, N., Zhu, X.X. (Frank), 2003. Value analysis of complex systems and industrial application to refineries. Industrial & Engineering Chemistry Research 42(21), 5165; Sadhukhan, J., Zhang, N., Zhu, X.X. (Frank), 2004. Analytical optimisation of industrial systems and applications to refineries, petrochemicals. Chemical Engineering Science 59(20), 4169; Sadhukhan, J., Smith, R., 2007. Synthesis of industrial systems based on value analysis. Computers & Chemical Engineering 31(5–6), 535] has been presented for investigating into the economic feasibility of biorefineries. The methodology devises a mechanism for systematic design of industrial systems based on comprehensive assessment of value on processing and cost of production, hence marginal contributions from individual processing routes and products. The feasibility of extracting value added products such as arabinoxylans (AX) from wheat bran within a wheat biorefinery principally producing ethanol has been investigated. Site-wide integrated flowsheets have been created by which AX can be extracted after recovering bran from wheat with ethanol production from the remaining wheat. Based on the most promising test case, value analysis shows that creating a market for AX is feasible in terms of production costs if the AX is co-produced with ethanol. A comprehensive value analysis that includes capital investment policies indicates that the required market price for AX to breakeven against conventional biorefineries without value added production is a strong function of plant life and this may vary between 4 and 6 £/kg for a plant life of 5–2 years, respectively. Further, it shows that if a market can be created for AX as a food ingredient with a selling price of 6 £/kg, the ethanol co-produced can be sold at 10% less than from a conventional biorefinery under current economic scenario.

Publisher Summary Cereals have risen to be the world's primary food source because they are energy-dense and non-perishable on storage, having their energy stored as starch in a desiccated state. However, their dry state makes harvested cereal grains unpalatable, while ungelatinized starch is unavailable to the human digestive system. Therefore, cereals must be processed to enhance their palatability and to make their nutrients available for digestion. Processing of cereals involves (i) separation of the components of the cereal grain, to enhance the scope for selection and combination of ingredients, facilitate processing and improve the quality, distinctiveness and appeal of end-products; and (ii) thermal processing to gelatinize starch, to develop attractive textures and flavors, and to render products dry and shelf-stable. Like much of the rest of the food industry, cereal processing for food uses can be broadly divided into primary processing and secondary processing. Opportunities for enhanced energy and water efficiency arise, in principle, within both primary and secondary processing of cereals. In practice, these opportunities may be limited. However, increasing energy costs are encouraging greater scrutiny of energy use within cereal processing and efficiency improvements can generate significant economic benefits. This chapter examines the major industrial cereal processes for food uses, with a view to identifying specific and generic opportunities for enhanced energy and water efficiency. The focus is on energy and water usage within the cereal processes themselves. Mixing, thermal processing, and cooling are identified as generic operations that offer potential for energy savings. The chapter discusses the implications for water and energy efficiency of future trends in cereal processing.